333 THE MULES. 



with a certain repugnance which many animals 

 manifest towards others very similar to themselves, 

 induced Buffon to draw the above mentioned con- 

 clusion. But he soon after could not help perceiv- 

 ing, that we can only pursue our inquiries with 

 certainty among a few domesticated species, some of 

 them expatriated, or under various conditions of 

 restraint, and that with all the others we depend 

 entirely upon inference." He discovered that there 

 were species, admitted to be distinct, which never- 

 theless produced fertile offspring : this was the case 

 in his later experiments with wolves and dogs, with 

 goats and sheep, and he was not then aware that 

 all these names include more than one species, which 

 there is every reason to believe can mix and pro- 

 duce fertile descendants, since several are already 

 known to possess the faculty. It was in endea- 

 vours to account for these exceptions that Buffon 

 was driven to arbitrary restrictions and extensions 

 of his rule ; and had he given due consideration to 

 the fact, first published by himself, of the different 

 number of mammae in different dogs, and known 

 that the vertebrae of the back, the sacrum, and tail 

 vary exceedingly in hogs, said by those who main- 

 tain the rigorous maxim before quoted to be of the 

 same species, he would most unquestionably have 

 framed his view of the law with more circumspec- 

 tion. 



As a general proposition, we do not mean to dis- 

 pute that it is still the best and most trustworthy 

 method for distinguishing species ; only the inferences 



